Checking, Openbullet

Featured in The Information
Checking 
Basically said you download an account list use a software (checker) that tries to
log into the account with your ip or proxy and if its correct it shows as a hit.

Openbullet 
Openbullet is one of the most popular program used for Checking accounts now day, very stable and up to date.

Its included many feature with GUI interface, easy to use